Geothermal ground source/water source heat exchange systems typically utilize fluid-filled closed loops of tubing buried in the ground, or submerged in a body of water, so as to either absorb heat from, or to reject heat into, the naturally occurring geothermal mass and/or water surrounding the buried or submerged fluid transport tubing. The tubing loop is extended to the surface and is then used to circulate one of the naturally warmed and naturally cooled fluid to an interior air heat exchange means.
Common and older design geothermal water-source heating/cooling systems typically circulate, via a water pump, a fluid comprised of water, or water with anti-freeze, in plastic (typically polyethylene) underground geothermal tubing so as to transfer geothermal heat to or from the ground in a first heat exchange step. Via a second heat exchange step, a refrigerant heat pump system is utilized to transfer heat to or from the water. Finally, via a third heat exchange step, an interior air handler (comprised of finned tubing and a fan) is utilized to transfer heat to or from the refrigerant to heat or cool interior air space.
Newer design geothermal DX heat exchange systems, where the refrigerant fluid transport lines are placed directly in the sub-surface ground and/or water, typically circulate a refrigerant fluid, such as R-22, R-410A, or the like, in sub-surface refrigerant lines, typically comprised of copper tubing, to transfer geothermal heat to or from the sub-surface elements via a first heat exchange step. DX systems only require a second heat exchange step to transfer heat to or from the interior air space, typically by means of an interior air handler. Consequently, DX systems are generally more efficient than water-source systems because less heat exchange steps are required and because no water pump energy expenditure is necessary. Further, since copper is a better heat conductor than most plastics, and since the refrigerant fluid circulating within the copper tubing of a DX system generally has a greater temperature differential with the surrounding ground than the water circulating within the plastic tubing of a water-source system, generally, less excavation and drilling is required, and installation costs are lower, with a DX system than with a water-source system.
While most in-ground/in-water DX heat exchange designs are feasible, various improvements have been developed intended to enhance overall system operational efficiencies. Several such design improvements, particularly in direct expansion/direct exchange geothermal heat pump systems, are taught in U.S. Pat. No. 5,623,986 to Wiggs; in U.S. Pat. No. 5,816,314 to Wiggs, et al.; in U.S. Pat. No. 5,946,928 to Wiggs; in U.S. Pat. No. 6,615,601 B1 to Wiggs; and in U.S. Pat. No. 6,932,149 to Wiggs, the disclosures of which are incorporated herein by reference. Such disclosures encompass both horizontally and vertically oriented sub-surface heat geothermal heat exchange means.
In any particular DX system design, as well as in other conventional heat pump system designs, increasing system operational efficiencies and helping to protect the longevity of system operational efficiencies are of paramount importance. The subject matter disclosed herein primarily relates to DX systems and various system design improvements that will increase system operational efficiencies and help to protect the longevity of system operational efficiencies.
Useful design improvements that will increase and help to protect the longevity of system operational efficiencies in a DX system, as well as in other conventional heat pump systems, would encompass an optimum means of oil return from an optimally designed oil separator and a means of maintaining a level of more than 1 and up to 10 degrees F. superheat, as measured in the suction line to the system's compressor, in the heating mode of operation. Generally, compressor manufacturers recommend operation at about 20 degrees F. superheat, so as to protect their compressors against “slugging”, occasioned by too much liquid refrigerant passing through the compressor. Slugging can damage compressors and impair operational efficiencies. To help to protect the longevity of system operational efficiencies in a DX System herein, as well as in other heat pump systems, means, among other obvious meanings, to help prevent operational efficiency degradation via at least one of short term and prolonged system operational use.
Consequently, a means to accomplish at least one of the said primary objectives would be preferable. The present disclosure provides a solution to these preferable objectives, as hereinafter more fully described.